In order to increase the power and data rates available from laser diodes, multi-element, individually addressable arrays of laser diodes are sometimes used. These can be of the diffraction-limited single-mode type or arrays of broad area emitters. The broad area emitters are diffraction-limited in one dimension, referred to as the “narrow” dimension and act as a wide area source in the other or “wide” dimension.
The advantage of the broad area emitters, also referred to as “stripe” laser diodes, is the much higher output power possible. Because of this high power, these devices are manufactured with their positive side bonded to a heat sink since the thermal conductivity of the substrate material is much lower than that of the heat sink. Since the connections to the individual diodes also have to come out of the positive side, there is a conflict and a compromise between the heat sinking needs and the interconnections.
U.S. Pat. No. 5,517,359 (Gelbart) depicts an apparatus for imaging light from a laser diode onto a multi-channel linear light valve. FIG. 1 shows a high power laser, wide emission area, laser diode 1 which emits a light beam 2 which is collimated in the vertical dimension by a cylindrical micro-lens 3. A second micro-lens 4 is a linear array of cylindrical lenslet arrays 4′ aligned with the multiple emitters l′ of laser diode 1. The light from cylindrical lenslet arrays 4′ is collimated by cylindrical lens 5 and imaged as a line on linear light valve 6.
When a high power laser is used, linear light valve 6 is a polarized lead zirconiom titanate (PLZT) device, causing the state of the polarization of the light to rotate when a voltage is applied to electrodes on the PLZT material. A polarizer prism 7 transmits the light of horizontal polarization and reflects the polarized light 11 with polarization changed by passing through the activated PLZT cells. An imaging lens 8 images linear light valve 6 onto heat sensitive or on light sensitive material 9, forming an image 10. Image 10 is a reduced image of the linear light valve 6.
The part designated as light pipe 104 in FIG. 1, shows an area where light propagates from lenslet array 4 in the direction of light valve 6. The light emitted from emitters 1′ through light pipe 104 may lose uniformity when it reaches light valve 6. An apparatus which overcomes the problem described above would be desirable.